Northwest Heat Wave and Cold Waves Back East

I am thinking of getting a palm tree for my house too!

I don't think it has escaped anyone's notice that is has been quite warm during the past four days...substantially above normal. Take a look at the temperatures since 25 December in the plot below for Seattle-Tacoma Airport. The time is in GMT (8hr later than PST) and the average daily highs and lows are shown by the red and blue lines. Since the new year began, our temps have been way above normal...with maximums getting near fifty and lows around 45. The average temps for this period are a high of 45 and a low of 36F. Our lows the last few days have generally been greater than the normal HIGHS. I am sweating just thinking about it. March temps in January.


Now at the same time the central and eastern U.S. is shivering under bitter cold temps--the media is full of cold wave and snowstorm coverage. Take a look at the max temps today across the U.S. in the graphic below. The west was balmy...50s in the NW to 70s in southern CA. The east coast was a different story..highest in the 20s and 30s in the NE and only in the very low 60s in southern FL. In the upper Midwest temps only rose into the single digits and teens.


This kind of pattern in which the west and east coasts are out of phase are not unusual at all. But why? The answer lies in the large scale circulation of the atmosphere ... something that is best seen aloft. The figure below shows conditions aloft at around half the pressure of the surface...this is a 500 millibar map (millibar is a unit of pressure) and it represents the height of this pressure above sea level. This pressure level is roughly at around 18,000 ft. The lines give you the height of this pressure surface above sea level. Where the heights are high there is a ridge, and where low, a trough. Winds tend to follow these lines with high heights to the right.
You will notice there is a ridge along the west coast and a broad trough over the eastern half of the country. Think of a rope held between two people...if one shakes it back and forth there is a wave-like pattern, with a ridge next to a trough. Generally, the nature of the flow is such that if we have a ridge they have a trough and vice versa..not always, but much of the time. On the western side of the trough the winds are blowing from the southwest and thus bring warm air northward, so the ridge tends to be warm. But on the back side of the ridge and western side of the trough the winds are from the north...bringing cold air southward, in this case into the eastern half of the U.S. We have been locked in this pattern for about a week...and with some minor changes it appears to be with us for a while.

And if you like warm here is more good news! The National Weather Service's Climate Prediction Center is going for a warmer than normal conditions for the remainder of the winter. Check out their graphic:
The major basis for this is the current El Nino..which brings warmer than normal temps to the northern tier of states..generally after Jan 1.

Perhaps we will have some early blossoms this year as a result of all this warmth...but I will leave that to the horticultural experts. I had a few plants savaged due to the cold wave in December, so hopefully we are finished with that!

Finally, the big weather of the meeting of the year is coming up...the Northwest Weather Workshop on March 5-6 in Seattle. This is where meteorologists and weather enthusiasts get together to talk about the weather of our region. So any of you could come. Information about the meeting, registration, fees, food, etc is found at:

http://www.atmos.washington.edu/pnww/

Any of you in the vineyard business or agricultural pursuits and might be interested in giving a talk on how weather affects you....let me know. We are thinking of a having a session on such matters.